Probing the Bright End of the Rest-frame Ultraviolet Luminosity Function at z = 8-10 with Hubble Pure-parallel Imaging

Looking for bright galaxies born in the early universe is fundamental to investigating the Epoch of Reionization, the era when the first stars and galaxies ionized the intergalactic medium. We utilize Hubble Space Telescope pure-parallel imaging to select galaxy candidates at a time 500-650 million years after the Big Bang, which corresponds to redshifts z ∼ 8-10. These data come from the Brightest of Reionizing Galaxies Survey (BoRG) Cycle 22 data set, which consists of pure-parallel imaging in ∼90 different lines of sight that sum up to an area of ∼420 arcmin2. This survey uses five filters and has the advantage (compared to the Cycle 21 BoRG program) of including imaging in the JH140 band, covering continuous wavelengths from the visible to near-infrared (λ = 0.35-1.7 m). This allows us to perform a reliable selection of galaxies at z ≥ 8 using the photometric-redshift technique. We use these galaxy candidates to constrain the bright end of the rest-frame ultraviolet luminosity function in this epoch. These candidates are excellent targets for follow-up observations, particularly with the James Webb Space Telescope.